The XO Directory

A recent study showed that earth was habitable 4.3 billion years ago - much more earlier than previously thought. The team of scientists led by geologists Takayuki Ushikubo, Valley and Noriko Kita analyzed ancient minerals called zircons. This mineral showed that liquid water existed as early as 4.3 billion years ago. Zircons, the tiny mineral grains, was used to determine the age of ancient rocks since this minerals are resistant to chemical change.

Ushikubo, the first author on the new study, says that atmospheric weathering could provide an answer to a long-standing question in geology: why no rock samples have ever been found dating back to the first 500 million years after the Earth formed.

"Currently, no rocks remain from before about 4 billion years ago," he says. "Some people consider this as evidence for very high temperature conditions on the ancient Earth."

Previous explanations for the missing rocks have included destruction by bombardment of meteorites and the possibility that the early Earth was a red-hot sea of magma in which rocks could not form.

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